1. Field of the Invention
This invention relates to a lubricant composition containing an alkoxylated amine salt of a dihydrocarbyldithiophosphoric acid and its use to improve fuel economy in an internal combustion engine.
2. Description of the Related Art
In order to protect internal combustion engines from wear, engine lubricating oils have been provided with antiwear and antioxidant additives. The primary oil additive for the past 40 years for providing antiwear and antioxidant properties has been zinc dialkyldithiophosphate (ZDDP). For example, U.S. Pat. No. 4,575,431 discloses a lubricating oil additive composition containing dihydrocarbyl hydrogen dithiophosphates and a sulfur-free of hydrocarbyl dihydrogen phosphates and dihydrocarbyl hydrogen phosphates, said composition being at least 50% neutralized by a hydrocarbyl amine having 10 to 30 carbons in said hydrocarbyl group. U.S. Pat. No. 4,089,790 discloses an extreme-pressure lubricating oil containing (1) hydrated potassium borate, (2) an antiwear agent selected from (a) ZDDP, (b) an ester, an amide or an amine salt of a dihydrocarbyl dithiophosphoric acid or (c) a zinc alkyl aryl sulfonate and (3) an oil-soluble organic sulfur compound.
Oil additive packages containing ZDDP have environmental drawbacks. ZDDP adds to engine deposits which can lead to increased oil consumption and emissions. Moreover, ZDDP is not ash-free. Various ashless oil additive packages have been developed recently due to such environmental concerns.
It would be desirable to have a lubricating oil additive which provides excellent antioxidant antiwear, fuel economy and environmentally beneficial (less fuel, i.e., less exhaust emissions) properties.